When working with an instrument in an area that is not visible, it may be important to determine and display the present orientation or position of the instrument. It is known in the art that it is possible to provide an instrument with electromagnetic position sensors, known as coil elements. A field generator arranged in the vicinity of the instrument generates an electromagnetic field which induces voltage within the coil elements or inductor of the instrument in accordance with the law of electromagnetic induction. The value or amplitude of the induced voltage or the electric currents in the coil elements may vary in accordance with the spatial orientation or situation and in accordance with the positioning of the sensors on the instrument. The electromagnetic situation sensors may also be so-called saturation core magnetometers which provide a signal that is proportional to the local field strength of the generated electromagnetic field.
A control unit interconnected with the field generator and the situation sensors may subsequently compute the position of the sensors and, thus, the position of the instrument from the measurement data from the field generator and the situation sensors. The position of the sensors may be displayed on, for example, a monitor.
Methods for determining the orientations or situations of instruments based on optical measurement principles using suitable sensors arranged on the instruments are also known.
Further, methods for failure detection are known for rigid instruments which do not deform during use. These methods for failure detection are based on the principle that two different sensors arranged on the instrument differently reference a certain area of the instrument at a point in time and hence determine different position data. That way, an erroneous measurement of at least one sensor is concluded. If such methods are used with instruments that deform during use the situation data of the deformed instrument may not unambiguously be distinguished from possible erroneous situation data. In particular, also due to the deformation of the instrument, situation data are considered to be erroneous, although there is no interference.
It is an object of the present invention to suggest a method that allows for detecting erroneously determined situation or position data of an instrument or their review.